Fig. 2: Förster coupling of moiré exciton wavepackets.
From: Förster valley-orbit coupling and topological lattice of hybrid moiré excitons
a Schematic of Coulomb exchange that annihilates an electron–hole pair in valley τ at layer n and creates one in valley \({\tau }^{{\prime} }\) of layer \({n}^{{\prime} }\). b The process in a effectively realizes non-local hopping—Förster coupling—of moiré exciton wavepackets, which is further determined by the envelope form (azimuthal quantum number m, wavepacket width w) of the intralayer component. c Förster coupling strength of various channels \({{\mathfrak{J}}}_{\tau ,m}^{{\tau }^{{\prime} },{m}^{{\prime} }}\), as function of in-plane distance (r) evaluated at out-of-plane distance z = 0. The subscripts (superscripts) denote the valley index τ (\({\tau }^{{\prime} }\)) and azimuthal index m (\({m}^{{\prime} }\)) of the initial (final) states. The inset shows the \({{\mathfrak{J}}}_{1,1}^{-1,-1}\) channel as function of the dimensionless in-plane and out-of-plane distances r/w, z/w. Wavepacket width w = 2 nm is used in calculation.
